The present disclosure relates to a neutralization device that irradiates an image carrier with neutralization light to discharge electricity of the image carrier, and to an electro-photographic image forming apparatus including the neutralization device.
In the electro-photographic image forming apparatus, cost reduction for the members is required, and downsizing of the housing of the apparatus is required. An exposure memory image generated on a surface of the photosensitive drum is required to be reduced for improving the performance of a photosensitive drum being an image carrier. In order to reduce generation of an exposure memory image, an area of the photosensitive drum after the transferring is required to be irradiated with neutralization light to discharge electricity on the surface of the photosensitive drum.
In general, a neutralization device is disposed between: a drum cleaning unit that removes attached matter such as toner remaining on the surface of the photosensitive drum; and a charging unit that charges the surface of the photosensitive drum. However, in a case in which the speed of forming an image is increased, the linear velocity (circumferential velocity) of the photosensitive drum is increased, and the period of time from the neutralization to the charging is significantly shortened. As a result, trapped carrier (charge) remains in a photosensitive layer of the photosensitive drum, and an exposure memory image causing deterioration of an image is likely to be generated.
For the purpose of suppressing generation of an exposure memory image, an image forming apparatus has been known, in which a neutralization device is disposed upstream from a cleaning device in a rotation direction of a photosensitive drum, so as to secure a period of time sufficient for eliminating trapped carrier between the neutralization and the charging.
In a case in which the neutralization device is disposed upstream from the cleaning device in the rotation direction of the photosensitive drum, the neutralization device is disposed in a position near downstream from the transfer unit. As a result, un-transferred toner that was not transferred on a sheet of paper and toner scattered after the transfer to the sheet of paper may attach to a light emitting portion being a neutralization light source of the neutralization device. For the purpose of suppressing attachment of toner to such a light emitting portion, a configuration is also employed in the conventional image forming apparatus, in which a partitioning member is provided between the conveyance path of a sheet of paper and the neutralization device, and an opened portion is formed between the partitioning member and the housing of the neutralization device, the opened portion being opened so as to face the surface of the photosensitive drum, and allowing neutralization light to pass therethrough.
However, in the conventional neutralization device, the space between the partitioning member and the housing of the neutralization device (i.e. the opened portion for allowing neutralization light to pass therethrough) is restricted by the size (diameter) of the photosensitive drum and by the conveyance path of a sheet of paper; therefore, it is difficult to secure a sufficient width in a circumferential direction of the photosensitive drum. As a result, the substrate, on which the light emitting portion of the neutralization device is mounted, is required to be disposed in parallel with the outer face of the housing.
In the conventional neutralization device, a base end side of the partitioning member is connected (fixed) to the housing, but another end side of the partitioning member is a free end. Therefore, in general, the free end of the opened portion of the partitioning member is composed of a thin and low-cost material (for example, resin), and thus is likely to bend toward the housing side. In particular, the free end of the partitioning member is likely to bend most significantly in its central portion in the longitudinal direction along an axial direction of the photosensitive drum. This brings about problems that: the opened portion is narrowed in its central portion of the photosensitive drum in the longitudinal direction along the axial direction; the quantity of neutralization light to be passed is reduced; and as a result, the distribution of the quantity of neutralization light is uneven along the axial direction of the photosensitive drum.